Recently, with higher output, higher efficiency and broader use of light-emitting elements such as light-emitting diodes (LED), luminaires have been developed using light-emitting elements which are expected to have a longer life. For example, LEDs are increasingly used as a light source of a downlight.
The light-emitting element such as the LED has a lower light output and a shorter service life as the temperature thereof increases. Therefore, for a luminaire using a solid-state light-emitting element such as LED or electroluminescent (EL) element as a light source, temperature rise of the light-emitting element needs to be restrained in order to extend the service life and to improve characteristics such as light-emitting efficiency.
Thus, in the luminaire using the LED as a light source, a light source unit is arranged on a front side (light irradiating side) of a heat-conductive main body and plural thermal radiation fins are provided on a rear side. Thus, thermal radiation performance is facilitated and temperature rise in the light-emitting element is restrained.